Spud assembly for a tank and method of attaching same



P 1959 H. L. EMMONS ETAL 2,903,562

v I SPUD ASSEMBLY FOR A TANK AND METHOD OF ATTACHING SAME Filed Sept. 13. 1956 a INVENTORS United States Patent Li SPUD.ASSEMBLY FOR A TANK AND METHOD J .()F A'ITACHING. SAME ,fIjI arold' L, Emmons, Kankakee, and-Joseph Maravolo, St.; An ne,' Ill., assignors to A. O; Smith Corporation, Milwaukee;'Wis., aycorporation of New York Applieatiion- September 13, 1956, Serial No. 609,635

2 Claims. (Cl. 219'-93) This .invention relates to a spud assembly. and .to a method. of attaching the same to a wall of atank or vessel.

1 In a tank such as a hot water heater, spuds aresecured within openings inthe tank .walL and provide a means for connectingthreadednipplesor pipesto the tank. As a hot water heater tank is generally made of ferrousmate- Irial and is subject to corrosion from the contained liquid, a cathodic protection system is employed to prevent the corrosion ofthe tank wall, and in orderto reduce the amount of exposed metal of the tank wall to be protected bythe cathodic system, the inner surface of'the-tank is generally lined with a coating of glass or vitreous enamel.

In coating. atank.with .glass, one of the biggest difliculties has arisen in coating the spud which projects into the interior of the'tank. More particularly, the inner corner orifilletrwherethe spudjoins thetankzwall and the inner rfedgeroft-heuspud are.diflicult.to satisfactorily coat..with glass. Inmany cases these areas arenot adequately .coatnedawiththe result thatthe amount .ofwbareor exposed Hnetalinthe tank.is.increased. and this,.of course, reduces a-the effective; life of. the anode.

'Q'The. present. invention. is. directed ;to.-. a spud assembly which eliminates all projections r on the j inside of the tank 4 and locates the spud solely on the ;outside of :the ;tank iwall. More specifically, the spudis provided with an :ppeningof substantially the same diameter as the opening in tankwall and the spud is disposed so that theopen- ,i ngs are. axially aligned. The spud is resistancewelded to 'the outer surface of the tank wall and a thread is formed in the annular surfaces of :the tank wall and the .spud which border the aligned openings so that.the thread" extends continuously from the inner surface of the tank Wall to the outer surface of the spud.

With this construction there is no projection on the inner surface of the tank with the result that the tank wall can be coated with glass and the glass coating will extend directly to the threaded opening.

In addition, the present spud construction is adapted for use on both heads and cylindrical shells of the tanks and therefore simplifies the manufacturing procedure over that of conventional practices in which different types of spuds are used for the heads and the shell.

The method of attaching the spud of the invention reduces the overall cost of the Water heater by decreasing welding problems and improving the assembly operations.

Furthermore, an improvement in the threads is obtained with the present invention because a harder steel can be employed for the spud and closer tolerances are possible on the inside diameter of the spud for tapping.

Other objects and advantages of the invention will appear in the course of the following description.

The accompanying drawing illustrates the best mode presently contemplated by the inventor for carrying out the invention.

In the drawing:

Figure 1 is a perspective View of the spud assembly as secured to a water heater head;

2,903,562 Patented Sept. 8 19.59

1 1 ,is formed .ofsheet metal and is adapted to enclosethe upper open end-of a cylindrical water; heater shell-or tank, not shown. The head 1. is formed witha generally flatportion 2 which is provided with, an opening 3. An annular spud 4, having an opening 5 correspondingin diameter to opening 3, is disposed in axialalignmentwith :opening 3 and is secured by weld 6 to the outer surface of head 1.

The inner annular surface. otthe spud. 4-bordering the opening 5 and the inner annular surface of thehead 1 bordering opening 3 are tappedto provide a thread'7 which extends continuously from the inner surface ofthe head 1 to, the outersurface of thespud 4. l

The inner surface of head 1 may be coatedwitha glass or vitreous enamel material 8 which extends to a position immediately adjacent the thread 7.

The,sp.ud itself, before beingwelded to the tank head 1,, isvforrned withthree annular-concentric ridges 9, 10 and 11. This is best shownrin Fig. 3. 'The central ridge .10,,has the greatest height of the ridges and isadapted toinitially contact the tank head 1 andfthis annular, biting contactprovides a small contact areafor accomplishing resistance welding of the spud to the tankwlall.

The,inner ridge 9. andthe outer ridge. 11 ,serve to con- .openings before the thread. 7 istappedtherein. Ridge' 9 under normal conditions traps. 'themetal. and eliminates .the rea i g operat n- As shown in Figs. 4 and 5,the dieassembly' for weldlower die 12 is provided with an axial recess 13 and a series of access openings 14 extend through the wall of the die 12 and communicate with the recess 13.

The upper end of the recess 13 receives a die plunger 15 and the plunger 15 is adapted to be inserted within the opening 3 in head 1 to align the head for welding.

The die plunger 15 is retained within recess 13 by a dowel pin 17 which extends through an opening 16 in the lower portion of plunger 15.

The die plunger 15 is biased upwardly by means of a spring 18 so that the upper end of the plunger projects upwardly beyond the upper surface of the lower die 12. Spring 18 extends between the bottom of recess 13 and the lower surface of plunger 15.

A movable upper die 19 is disposed in axial alignment with lower die 12 and is provided with an axial recess 20 which receives a plunger pin 21. The outer end of pin 21 extends a substantial rdistance beyond the lower surface of die 19. Pin 21 is maintained out of electrical contact with the upper die 19 by an insulating material 22 which is disposed within the recess 20.

Electrical energy is supplied to the dies 12 and 19 by leads, not shown so that when the upper die 19 mashes spud 4 against tank head 1, a current will flow between the dies to heat the spud and the tank head.

In operation, the opening 3 in head 1 is initially pierced by conventional procedures. The head 1 is then placed on the lower die 12 so that the die plunger 15 projects through the opening 3 in the head.

The spud 4 is then placed around the upper end of the die plunger 15 with the ridges 10 bearing against the outer surface of the head 1. The inner diameter of the spud 4 and the opening 3 have a diameter which is slightly greater than the diameter of plunger 15 so that the openings 3 and are disposed in substantial axial alignment.

The upper die 19 is then moved downwardly and electrical energy is supplied to the dies. As the upper die 19 moves downwardly, plunger pin 21 held therein contacts the upper surface of die plunger 15 forcing plunger 15 downwardly against the force of spring 18. Further downward movement of the upper die brings the lower surface 23 of die 19 into contact with the spud 4 and mashes the spud into the tank head 1 which is held firmly against the upper surface 24 of lower die 12.

After a suflicient time to weld the spud to the head, the upper die is moved upwardly and the welded article is removed from the lower die.

The openings 3 and 5 are then tapped by conventional procedures to provide the thread 7 which extends from the inner surface of the tank 1 to the outer surface of spud 4.

After tapping, the inner surface of the head is coated with the glass composition 8 and fired at an elevated temperature to fuse the glass to the head.

The present invention provides a spud assembly which eliminates all projections on the inner surface of a tank and thereby substantially eliminates the problems connected with glass coating of conventional spud structures. Furthermore, as the head wall is threaded and thereby contributes to the total length of the thread, the spud itself can be reduced in thickness and this provides a material savings.

While the above description is directed to the attachment of the spud to a tank head, it is contemplated that the spud may be attached to a cylindrical shell or any other portion of the wall of a tank or vessel. Similarly, while the above procedure described the glass coating being applied to the head after the thread 7 is tapped, it is contemplated that the procedure can be reversed so that glass coating 8 is applied and fused to the tank wall before the thread 7 is tapped.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. In a method of fabricating a hot water storage tank, the steps of forming an opening in a wall of the tank, securing an annular spud to the outer surface of said wall in concentric relation to the opening in said wall, tapping a thread through the opening in the spud and through the opening in the tank wall with the thread extending substantially continuously from the inner surface of the tank wall to the outer surface of the spud, and coating the inner surface of the wall to the edge of the opening therein with a vitreous enamel composition, said spud being located wholely on the outer surface of the wall serving to maintain the inner surface of the wall substantially free of projections and facilitate application of said vitreous enamel composition.

2. In a method of fabricating a head for a hot water storage tank, the steps of forming an opening in said head, welding an annular spud to the outer surface of said head, said spud having a central opening of substantially similar diameter to the opening in said head and said opening in said spud being disposed in alignment with the opening in said head, tapping a thread through the aligned openings with the thread extending substantially continuously from the inner surface of the head to the outer surface of the spud, and coating the inner surface of the head to the edge of said opening therein with a vitreous enamel composition, said spud being located wholely on the outer surface of the head serving to eliminate internal projections and facilitate application of said vitreous enamel composition.

References Cited in the file of this patent UNlTED STATES PATENTS 1,004,795 Lachman Oct. 3, 1911 2,054,187 Almdale Sept. 15, 1936 2,268,343 Phillips Dec. 30, 1941 2,306,180 Myers et al Dec. 22, 1942 2,360,359 Myers et al. Oct. 17, 1944 2,361,636 Koppel Oct. 31, 1944 2,362,983 Bodnar et al Nov. 21, 1944 2,372,772 Ellis et al. Apr. 3, 1945 2,471,475 Andrus May 31, 1949 2,528,280 Lyon Oct. 31, 1950 2,537,678 Koetting Jan. 9, 1951 2,731,535 Grey Jan. 17, 1956 2,822,461 Lyon Feb. 4, 1958 FOREIGN PATENTS 832,632 France July 4, 1938 

